Flip-chip assembly, also known as direct chip attachment, is a method for electrically connecting a die directly to a substrate. In flip-chip assembly, conductive bumps are attached to an upper surface of a die. The die is then flipped over and placed face down on top of and in contact with the substrate in order to establish an electrical connection. In contrast, other assembly methods use wire bonds to connect the die to the substrate. These alternative assembly methods require the die to be attached to the substrate face up, and wires to be bonded to the die, then looped and electrically connected to the substrate.
Incorporating flip-chip technology in the semiconductor device manufacturing process offers a number of advantages over using standard assembly methods. These advantages include decreasing the size of the footprint of the device, while increasing performance, flexibility, and reliability. The use of flip-chip technology eliminates the space needed for wire bonding and die surface area of a package, which essentially reduces the overall size of the package. In addition, the elimination of wire connections and implementation of a shorter electrical path from the die to the substrate by way of a conductive bump connection reduces inductance and capacitance.
The flip-chip method is also more flexible than the standard methods of assembly. Flip-chip technology allows use of the entire surface area of the die for the conductive bump connections, whereas standard methods using wire bond connections are generally limited to the perimeter of the die. Therefore, to achieve a comparable number of connections, the die size for a standard method of assembly would have to be greatly increased. Lastly, an adhesive underfill material may be placed between the die and the substrate to increase mechanical reliability.
With the increasing demand for flip-chip technology in the semiconductor manufacturing industry, there is a need to further improve the connection between the flip-chip die and the substrate in a flip-chip assembly. There is a need to increase the density of interconnects to accommodate the ever increasing number of connection points and ever decreasing size of the flip-chip die. There is also a need to increase the stability, thermal performance, and integrity of the flip-chip assembly.